firebase tutorial-modifier private is not allowed here

I'm attempting to add login functionality to my android app using Firebase. I'm following the instructions at https://firebase.google.com/docs/auth/android/password-auth, but when I attempt to use the private modifier, Android Studio tells me it's "not allowed here." But if I don't use that modifier, I can't call mAuth in onStart.

That's basic Java rule. You cannot use private, public, protected keywords inside methods. You can only set the visibility of a "global" variable as you did for private FirebaseAuth.AuthStateListener mAuthListener;.